How to generate a plane that fills the whole ARView?

I am writing a small RealityKit app which watches for a specific image, and when the image is seen and then disappears, it starts a video playing (a plane with VideoMaterial).

I'm using the height and width of the recognized image as the size of the mesh for the plane, but I would really like for the plane to fill the whole available space. Unfortunately, the ARView's frame is given in points, but the size of the mesh needs to be in meters.

I can't find any way to make this conversion. Is what I want to do possible?

How to generate a plane that fills the whole ARView?
 
 
Q